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library(priorsense)
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library(bayestestR)
df <- read_xlsx("hair_cort_dog_all.xlsx", col_types = c("text", "text",
"text", "text", "text", "text",
"text", "numeric","text", "skip",
"numeric", "skip", "skip",
"numeric", "skip"))
df <- as.data.frame(df)
dim(df) # will tell you how many rows and columns the dataset has
## [1] 73 11
class(df) # will tell you what data structure has the dataset been assigned
## [1] "data.frame"
head(df)
## number group visit season breed_group coat_colour sex age comorbidity
## 1 c1 stopped v0 winter ret dark Male 43 yes
## 2 c2 stopped v0 autumn mix dark Male 105 yes
## 3 c3 stopped v0 spring ckcs mix Female 117 yes
## 4 c4 stopped v0 summer ret dark Female 108 yes
## 5 c5 stopped v0 summer ret dark Female 110 yes
## 6 c6 stopped v0 winter mix light Female 120 yes
## fat_percent cortisol
## 1 52.21393 4.924220
## 2 38.52059 7.304202
## 3 46.94916 1.590000
## 4 44.46813 0.861570
## 5 39.59363 6.217317
## 6 NA 4.426785
numeric_df <- Filter(is.numeric, df)
describe(numeric_df) # the describe function in psych provides summary stats
## # A tibble: 3 × 26
## described_variables n na mean sd se_mean IQR skewness kurtosis
## <chr> <int> <int> <dbl> <dbl> <dbl> <dbl> <dbl> <dbl>
## 1 age 73 0 95.8 35.6 4.16 44 -0.104 -0.00589
## 2 fat_percent 55 18 40.5 7.82 1.05 7.82 -0.294 1.12
## 3 cortisol 73 0 8.11 16.5 1.93 5.43 4.05 18.7
## # ℹ 17 more variables: p00 <dbl>, p01 <dbl>, p05 <dbl>, p10 <dbl>, p20 <dbl>,
## # p25 <dbl>, p30 <dbl>, p40 <dbl>, p50 <dbl>, p60 <dbl>, p70 <dbl>,
## # p75 <dbl>, p80 <dbl>, p90 <dbl>, p95 <dbl>, p99 <dbl>, p100 <dbl>
plot_normality(numeric_df)
apply(numeric_df, 2, shapiro.test)
## $age
##
## Shapiro-Wilk normality test
##
## data: newX[, i]
## W = 0.97361, p-value = 0.1288
##
##
## $fat_percent
##
## Shapiro-Wilk normality test
##
## data: newX[, i]
## W = 0.97956, p-value = 0.4692
##
##
## $cortisol
##
## Shapiro-Wilk normality test
##
## data: newX[, i]
## W = 0.46269, p-value = 6.756e-15
qqnorm(df$cortisol)
qqline(df$cortisol, col = "red")
qqnorm(log(df$cortisol))
qqline(log(df$cortisol), col = "red")
shapiro.test(log(df$cortisol))
##
## Shapiro-Wilk normality test
##
## data: log(df$cortisol)
## W = 0.94725, p-value = 0.004126
summary(df$cortisol)
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## 0.4141 1.4119 2.3331 8.1089 6.8455 104.6172
summary(log(df$cortisol))
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## -0.8817 0.3449 0.8472 1.1816 1.9236 4.6503
df$lgCort <- log(df$cortisol)
summary(df$lgCort)
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## -0.8817 0.3449 0.8472 1.1816 1.9236 4.6503
hist(df$lgCort)
df$breed <- df$breed_group
df$breed <- factor(df$breed, levels = c("mix", "ckcs", "pug", "ret", "other"))
head(df$breed)
## [1] ret mix ckcs ret ret mix
## Levels: mix ckcs pug ret other
sumtable(df)
| Variable | N | Mean | Std. Dev. | Min | Pctl. 25 | Pctl. 75 | Max |
|---|---|---|---|---|---|---|---|
| group | 73 | ||||||
| … completed | 42 | 58% | |||||
| … stopped | 31 | 42% | |||||
| visit | 73 | ||||||
| … v0 | 52 | 71% | |||||
| … v1 | 21 | 29% | |||||
| season | 73 | ||||||
| … autumn | 21 | 29% | |||||
| … spring | 14 | 19% | |||||
| … summer | 22 | 30% | |||||
| … winter | 16 | 22% | |||||
| breed_group | 73 | ||||||
| … ckcs | 7 | 10% | |||||
| … mix | 16 | 22% | |||||
| … other | 26 | 36% | |||||
| … pug | 7 | 10% | |||||
| … ret | 17 | 23% | |||||
| coat_colour | 73 | ||||||
| … dark | 30 | 41% | |||||
| … light | 28 | 38% | |||||
| … mix | 15 | 21% | |||||
| sex | 73 | ||||||
| … Female | 43 | 59% | |||||
| … Male | 30 | 41% | |||||
| age | 73 | 96 | 36 | 16 | 73 | 117 | 182 |
| comorbidity | 73 | ||||||
| … no | 15 | 21% | |||||
| … yes | 58 | 79% | |||||
| fat_percent | 55 | 40 | 7.8 | 18 | 37 | 45 | 61 |
| cortisol | 73 | 8.1 | 16 | 0.41 | 1.4 | 6.8 | 105 |
| lgCort | 73 | 1.2 | 1.2 | -0.88 | 0.34 | 1.9 | 4.7 |
| breed | 73 | ||||||
| … mix | 16 | 22% | |||||
| … ckcs | 7 | 10% | |||||
| … pug | 7 | 10% | |||||
| … ret | 17 | 23% | |||||
| … other | 26 | 36% |
par(mfrow = c(1,1))
vioplot(lgCort ~ breed, col = "firebrick",
data = df)
stripchart(lgCort ~ breed, vertical = TRUE, method = "jitter",
col = "steelblue3", data = df, pch = 20)
df$slgCort <- standardize(df$lgC)
summary(df$slgCort)
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## -1.7079 -0.6925 -0.2768 0.0000 0.6142 2.8713
hist(df$slgCort)
df2 <- na.omit(df)
model <- brm(slgCort ~ breed + (1 | visit), family = skew_normal(), data = df2)
default_prior(slgCort ~ breed + (1 | visit),
family = skew_normal(),
data = df2)
## prior class coef group resp dpar nlpar lb ub
## normal(0, 4) alpha
## (flat) b
## (flat) b breedckcs
## (flat) b breedother
## (flat) b breedpug
## (flat) b breedret
## student_t(3, -0.1, 2.5) Intercept
## student_t(3, 0, 2.5) sd 0
## student_t(3, 0, 2.5) sd visit 0
## student_t(3, 0, 2.5) sd Intercept visit 0
## student_t(3, 0, 2.5) sigma 0
## source
## default
## default
## (vectorized)
## (vectorized)
## (vectorized)
## (vectorized)
## default
## default
## (vectorized)
## (vectorized)
## default
No published data about effects on breed, but this is plausible However, unclear as to which breeds will differ and which way. Therefore, use a regularising prior but keep it neutral and broad.
# Set individual priors
prior_int <- set_prior("normal(0, 0.5)", class = "Intercept")
prior_sig <- set_prior("exponential(1)", class = "sigma")
prior_b <- set_prior("normal(0, 1)", class = "b")
prior_sd <- set_prior("normal(0, 1)", class = "sd")
prior_alpha <- set_prior("normal(4, 8)", class = "alpha")
# Combine priors into list
priors <- c(prior_int, prior_sig, prior_b, prior_sd, prior_alpha)
x <- seq(-3, 3, length.out = 100)
y <- dnorm(x, mean = 0, sd = 1)
plot(y ~ x, type = "l")
x <- seq(0, 3, length.out = 100)
y <- dexp(x, rate = 0.5)
plot(y ~ x, type = "l")
Based on distribution of log normal hair cortisol, expect things to be skewed to the right. Try different levels of alpha for skew normal.
x <- seq(-3, 5, length.out = 100)
y <- dskew_normal(x, mu = 0, sigma = 1, alpha = 4)
plot(y ~ x, type = "l")
So, expect alpha to be positive… perhaps 4, but keep sd broad to allow some flexibility
x <- seq(0, 5, length.out = 100)
y <- dnorm(x, mean = 0, sd = 2)
plot(y ~ x, type = "l")
x <- seq(-3, 3, length.out = 100)
y <- dnorm(x, mean = 0, sd = 1.0)
plot(y ~ x, type = "l")
Increased adapt_delta >0.8 (0.9 here), as had divergent transitions
set.seed(666)
model <- brm(slgCort ~ breed + (1 | visit),
family = skew_normal(),
data = df,
prior = priors,
control=list(adapt_delta=0.99999999, stepsize = 0.001, max_treedepth = 15),
iter = 8000, warmup = 2000,
cores = 4,
save_pars = save_pars(all =TRUE),
sample_prior = TRUE)
## Compiling Stan program...
## Trying to compile a simple C file
## Running /Library/Frameworks/R.framework/Resources/bin/R CMD SHLIB foo.c
## using C compiler: ‘Apple clang version 17.0.0 (clang-1700.0.13.5)’
## using SDK: ‘MacOSX15.5.sdk’
## clang -arch arm64 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/Rcpp/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/unsupported" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/BH/include" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/src/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppParallel/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/rstan/include" -DEIGEN_NO_DEBUG -DBOOST_DISABLE_ASSERTS -DBOOST_PENDING_INTEGER_LOG2_HPP -DSTAN_THREADS -DUSE_STANC3 -DSTRICT_R_HEADERS -DBOOST_PHOENIX_NO_VARIADIC_EXPRESSION -D_HAS_AUTO_PTR_ETC=0 -include '/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/stan/math/prim/fun/Eigen.hpp' -D_REENTRANT -DRCPP_PARALLEL_USE_TBB=1 -I/opt/R/arm64/include -fPIC -falign-functions=64 -Wall -g -O2 -c foo.c -o foo.o
## In file included from <built-in>:1:
## In file included from /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/stan/math/prim/fun/Eigen.hpp:22:
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## In file included from /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/Eigen/Core:19:
## /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/Eigen/src/Core/util/Macros.h:679:10: fatal error: 'cmath' file not found
## 679 | #include <cmath>
## | ^~~~~~~
## 1 error generated.
## make: *** [foo.o] Error 1
## Start sampling
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
summary(model)
## Family: skew_normal
## Links: mu = identity; sigma = identity; alpha = identity
## Formula: slgCort ~ breed + (1 | visit)
## Data: df (Number of observations: 73)
## Draws: 4 chains, each with iter = 8000; warmup = 2000; thin = 1;
## total post-warmup draws = 24000
##
## Multilevel Hyperparameters:
## ~visit (Number of levels: 2)
## Estimate Est.Error l-95% CI u-95% CI Rhat Bulk_ESS Tail_ESS
## sd(Intercept) 0.37 0.36 0.01 1.36 1.00 7556 9552
##
## Regression Coefficients:
## Estimate Est.Error l-95% CI u-95% CI Rhat Bulk_ESS Tail_ESS
## Intercept -0.10 0.30 -0.71 0.51 1.00 10616 11125
## breedckcs 0.14 0.38 -0.65 0.84 1.00 13139 14313
## breedpug 0.19 0.36 -0.55 0.85 1.00 14815 14562
## breedret 0.09 0.28 -0.49 0.62 1.00 12104 15143
## breedother 0.10 0.26 -0.39 0.62 1.00 14704 14362
##
## Further Distributional Parameters:
## Estimate Est.Error l-95% CI u-95% CI Rhat Bulk_ESS Tail_ESS
## sigma 1.04 0.10 0.87 1.27 1.00 14360 14487
## alpha 5.35 3.34 1.57 14.44 1.00 10117 6858
##
## Draws were sampled using sampling(NUTS). For each parameter, Bulk_ESS
## and Tail_ESS are effective sample size measures, and Rhat is the potential
## scale reduction factor on split chains (at convergence, Rhat = 1).
plot(model)
Looking for hairy caterpillars
mcmc_plot(model, type = 'rank_overlay')
Usually better than the compatability intervals given in the summary ### a. ckcs
draws <- as.matrix(model)
HPDI(draws[,2], 0.97) # 2nd column is draws for ckcs
## |0.97 0.97|
## -0.7183886 0.9231527
draws <- as.matrix(model)
HPDI(draws[,3], 0.97) # 3rd column is draws for pug
## |0.97 0.97|
## -0.5865707 0.9615309
draws <- as.matrix(model)
HPDI(draws[,4], 0.97) # 4th column is draws for ret
## |0.97 0.97|
## -0.5195171 0.7023931
draws <- as.matrix(model)
HPDI(draws[,5], 0.97) # 5th column is draws for other
## |0.97 0.97|
## -0.4649280 0.6533254
bayes_R2(model, probs = c(0.015, 0.5, 0.985)) # 0.015, 0.5, 0.985 are the quantiles
## Estimate Est.Error Q1.5 Q50 Q98.5
## R2 0.04642802 0.02818366 0.006334857 0.04108256 0.1281878
loo_R2(model, probs = c(0.015, 0.5, 0.985)) # 0.015, 0.5, 0.985 are the quantiles
## Warning: Some Pareto k diagnostic values are too high. See help('pareto-k-diagnostic') for details.
## Estimate Est.Error Q1.5 Q50 Q98.5
## R2 -0.08681619 0.03212178 -0.179703 -0.08211637 -0.03317327
checks whether actual data is similar to simulated data.
pp_check(model, ndraws = 100)
par(mfrow = c(1,1))
pp_check(model, type = "hist", ndraws = 11, binwidth = 0.25) # separate histograms of 11 MCMC draws vs actual data
pp_check(model, type = "error_hist", ndraws = 11) # separate histograms of errors for 11 draws
## `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.
pp_check(model, type = "scatter_avg", ndraws = 100) # scatter plot
pp_check(model, type = "stat_2d") # scatterplot of joint posteriors
## Using all posterior draws for ppc type 'stat_2d' by default.
## Note: in most cases the default test statistic 'mean' is too weak to detect anything of interest.
# PPC functions for predictive checks based on (approximate) leave-one-out (LOO) cross-validation
pp_check(model, type = "loo_pit_overlay", ndraws = 1000)
## Warning: Found 2 observations with a pareto_k > 0.7 in model '.x1'. We
## recommend to set 'moment_match = TRUE' in order to perform moment matching for
## problematic observations.
## NOTE: The kernel density estimate assumes continuous observations and is not optimal for discrete observations.
pp_check(model, type = "error_scatter_avg")
## Using all posterior draws for ppc type 'error_scatter_avg' by default.
pairs(model)
loo_model <- loo(model, moment_match = TRUE)
loo_model
##
## Computed from 24000 by 73 log-likelihood matrix.
##
## Estimate SE
## elpd_loo -105.1 6.1
## p_loo 6.8 1.6
## looic 210.2 12.2
## ------
## MCSE of elpd_loo is 0.1.
## MCSE and ESS estimates assume MCMC draws (r_eff in [0.4, 1.1]).
##
## All Pareto k estimates are good (k < 0.7).
## See help('pareto-k-diagnostic') for details.
First, check the sensitivity of the prior and likelihood to power-scaling. Posterior and posteriors resulting from power-scaling.
powerscale_sensitivity(model, variable = c("b_Intercept", "b_breedckcs", "b_breedother", "b_breedpug", "b_breedret"), , facet_rows = "variable")
## Sensitivity based on cjs_dist
## Prior selection: all priors
## Likelihood selection: all data
##
## variable prior likelihood diagnosis
## b_Intercept 0.041 0.037 -
## b_breedckcs 0.025 0.088 -
## b_breedother 0.019 0.078 -
## b_breedpug 0.021 0.092 -
## b_breedret 0.028 0.068 -
powerscale_plot_dens(model, variable = c("b_Intercept", "b_breedckcs", "b_breedother", "b_breedpug", "b_breedret"), facet_rows = "variable")
check_prior(model, effects = "all")
## Parameter Prior_Quality
## 1 b_Intercept informative
## 2 b_breedckcs informative
## 3 b_breedpug informative
## 4 b_breedret informative
## 5 b_breedother informative
## 6 sd_visit__Intercept informative
Can simulate data just on the priors. Fit model but only consider prior when fitting model. If this looks reasonable, it helps to confirm that your priors were reasonable
set.seed(666)
model_priors_only <- brm(slgCort ~ breed + (1 | visit),
family = skew_normal(),
prior = priors,
data = df,
sample_prior = "only")
## Compiling Stan program...
## Trying to compile a simple C file
## Running /Library/Frameworks/R.framework/Resources/bin/R CMD SHLIB foo.c
## using C compiler: ‘Apple clang version 17.0.0 (clang-1700.0.13.5)’
## using SDK: ‘MacOSX15.5.sdk’
## clang -arch arm64 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/Rcpp/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/unsupported" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/BH/include" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/src/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppParallel/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/rstan/include" -DEIGEN_NO_DEBUG -DBOOST_DISABLE_ASSERTS -DBOOST_PENDING_INTEGER_LOG2_HPP -DSTAN_THREADS -DUSE_STANC3 -DSTRICT_R_HEADERS -DBOOST_PHOENIX_NO_VARIADIC_EXPRESSION -D_HAS_AUTO_PTR_ETC=0 -include '/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/stan/math/prim/fun/Eigen.hpp' -D_REENTRANT -DRCPP_PARALLEL_USE_TBB=1 -I/opt/R/arm64/include -fPIC -falign-functions=64 -Wall -g -O2 -c foo.c -o foo.o
## In file included from <built-in>:1:
## In file included from /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/stan/math/prim/fun/Eigen.hpp:22:
## In file included from /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/Eigen/Dense:1:
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## /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/Eigen/src/Core/util/Macros.h:679:10: fatal error: 'cmath' file not found
## 679 | #include <cmath>
## | ^~~~~~~
## 1 error generated.
## make: *** [foo.o] Error 1
## Start sampling
##
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pp_check(model_priors_only, ndraws = 100)
as_draws_df(model) %>%
select(b_Intercept:sigma) %>%
cov() %>%
round(digits = 3)
## Warning: Dropping 'draws_df' class as required metadata was removed.
## b_Intercept b_breedckcs b_breedpug b_breedret b_breedother
## b_Intercept 0.090 -0.036 -0.035 -0.037 -0.036
## b_breedckcs -0.036 0.144 0.035 0.043 0.034
## b_breedpug -0.035 0.035 0.126 0.035 0.034
## b_breedret -0.037 0.043 0.035 0.080 0.034
## b_breedother -0.036 0.034 0.034 0.034 0.066
## sd_visit__Intercept -0.001 -0.005 -0.002 -0.003 0.000
## sigma 0.005 0.003 0.000 0.003 -0.001
## sd_visit__Intercept sigma
## b_Intercept -0.001 0.005
## b_breedckcs -0.005 0.003
## b_breedpug -0.002 0.000
## b_breedret -0.003 0.003
## b_breedother 0.000 -0.001
## sd_visit__Intercept 0.132 -0.001
## sigma -0.001 0.010
NB Uses posterior_predict
# use posterior predict to simulate predictions
ppd <- posterior_predict(model)
par(mfrow = c(2,2))
stripchart(slgCort ~ breed, vertical = TRUE, method = "jitter",
col = "steelblue3", data = df, pch = 20, main = "Observed")
stripchart(ppd[sample(seq(1, dim(ppd)[1]), 1),] ~ breed, vertical = TRUE, method = "jitter",
col = "firebrick3", data = df, pch = 20, main = "PPD")
stripchart(ppd[sample(seq(1, dim(ppd)[1]), 1),] ~ breed, vertical = TRUE, method = "jitter",
col = "firebrick3", data = df, pch = 20, main = "PPD")
stripchart(ppd[sample(seq(1, dim(ppd)[1]), 1),] ~ breed, vertical = TRUE, method = "jitter",
col = "firebrick3", data = df, pch = 20, main = "PPD")
plot(conditional_effects(model), ask = FALSE)
ce <- conditional_effects(model, effects = "breed")
ce_df <- ce[[1]][c(1, 6:9)]
ggplot(ce_df, aes(x=breed, y=estimate__, group=1)) +
geom_errorbar(width=.1, aes(ymin=lower__, ymax=upper__), colour=c("#F8766D", "#A3A500","#00BF7D",
"#00B0F6", "#E776F3"), linewidth = 1) +
geom_point(shape=21, size=6, fill=c("#F8766D", "#A3A500","#00BF7D",
"#00B0F6", "#E776F3")) +
theme_bw() +
labs(title = "Conditional effect of breed on hair cortisol") +
labs(y = paste0("Log Hair Cortisol (standardised)")) +
labs(x = paste0("breed")) +
theme(axis.title.y = element_text(size=12, face="bold"),
axis.title.x = element_text(size=12, face="bold"),
title = element_text(size=12, face="bold"),
plot.title = element_text(hjust = 0.5),
axis.text.x = element_text(color = "grey25", size = 12),
axis.text.y = element_text(color = "grey50", size = 10))
mcmc_plot(model,
variable = c(
"b_breedckcs",
"b_breedpug",
"b_breedret",
"b_breedother"))
mcmc_plot(model, variable = c(
"b_Intercept",
"sigma",
"b_breedckcs",
"b_breedpug",
"b_breedret",
"b_breedother"))
posterior <- as.matrix(model)
mcmc_areas(posterior,
pars = c("b_Intercept", "sigma",
"b_breedckcs",
"b_breedpug",
"b_breedret",
"b_breedother"),
# arbitrary threshold for shading probability mass
prob = 0.75)
posterior <- as.matrix(model)
mcmc_areas(posterior,
pars = c("b_breedckcs",
"b_breedpug",
"b_breedret",
"b_breedother"),
prob = 0.75) # arbitrary threshold for shading probability mass
# Focus on describing posterior
hdi_range <- hdi(model, ci = c(0.65, 0.70, 0.80, 0.89, 0.95))
plot(hdi_range, show_intercept = T)
draws <- as.matrix(model)
mean(draws[,2] >0)
## [1] 0.663375
mean(draws[,2] <0)
## [1] 0.336625
HPDI(draws[,2], prob=0.97)
## |0.97 0.97|
## -0.7183886 0.9231527
draws <- as.matrix(model)
mean(draws[,3] >0)
## [1] 0.7124167
mean(draws[,3] <0)
## [1] 0.2875833
HPDI(draws[,3], prob=0.97)
## |0.97 0.97|
## -0.5865707 0.9615309
draws <- as.matrix(model)
mean(draws[, 4] >0)
## [1] 0.6295417
mean(draws[, 4] <0)
## [1] 0.3704583
HPDI(draws[, 4], prob=0.97)
## |0.97 0.97|
## -0.5195171 0.7023931
draws <- as.matrix(model)
mean(draws[, 5] >0)
## [1] 0.6539583
mean(draws[, 5] <0)
## [1] 0.3460417
HPDI(draws[, 5], prob=0.97)
## |0.97 0.97|
## -0.4649280 0.6533254
# create new dataframe which contains results of the first dog
new_data <- rbind(df[1,], df[1,], df[1,], df[1,], df[1,])
# Now change one category to be different
new_data$breed <- c("mix", "ckcs", "pug", "ret", "other")
# Visualise df to make sure it has worked
new_data
## number group visit season breed_group coat_colour sex age comorbidity
## 1 c1 stopped v0 winter ret dark Male 43 yes
## 2 c1 stopped v0 winter ret dark Male 43 yes
## 3 c1 stopped v0 winter ret dark Male 43 yes
## 4 c1 stopped v0 winter ret dark Male 43 yes
## 5 c1 stopped v0 winter ret dark Male 43 yes
## fat_percent cortisol lgCort breed slgCort
## 1 52.21393 4.92422 1.594166 mix 0.3415375
## 2 52.21393 4.92422 1.594166 ckcs 0.3415375
## 3 52.21393 4.92422 1.594166 pug 0.3415375
## 4 52.21393 4.92422 1.594166 ret 0.3415375
## 5 52.21393 4.92422 1.594166 other 0.3415375
# Now get mean predictions from the draws of the model
pred_means <- posterior_predict(model, newdata = new_data)
# Compare difference in means for each breedversus mix
differenceCKCS <- pred_means[,1] - pred_means[,2]
differencePug <- pred_means[,1] - pred_means[,3]
differenceRet <- pred_means[,1] - pred_means[,4]
differenceOther <- pred_means[,1] - pred_means[,5]
par(mfrow = c(2,2))
# Examine mean of difference
mean(differenceCKCS)
## [1] -0.1259493
# View histogram of this
hist(differenceCKCS)
# Create HPDI
HPDI(differenceCKCS, 0.93)
## |0.93 0.93|
## -2.994134 2.651799
# Examine mean of difference
mean(differencePug)
## [1] -0.1750287
# View histogram of this
hist(differencePug)
# Create HPDI
HPDI(differencePug, 0.93)
## |0.93 0.93|
## -2.889368 2.680507
# Examine mean of difference
mean(differenceRet)
## [1] -0.07779497
# View histogram of this
hist(differenceRet)
# Create HPDI
HPDI(differenceRet, 0.93)
## |0.93 0.93|
## -2.855377 2.673152
# Examine mean of difference
mean(differenceOther)
## [1] -0.08386029
# View histogram of this
hist(differenceOther)
# Create HPDI
HPDI(differenceOther, 0.93)
## |0.93 0.93|
## -2.805863 2.691576
# create new dataframe which contains results of all dogs
new_data1 <- df
# Now change one category to be different
new_data1$breed_group <- c("mix")
# create new dataframe which contains result sof all dogs
new_data2 <- df
# Now change one category to be different
new_data2$breed_group <- c("ckcs")
# Now get predictions from the draws of the models
pred_nd1 <- posterior_predict(model, newdata = new_data1)
pred_nd2 <- posterior_predict(model, newdata = new_data2)
pred_diff <- pred_nd1 - pred_nd2
pred_diff <- data.frame(pred_diff)
# Create mean of differences for each column (dog) of the dataframe
pred_diff_ckcs <- apply(pred_diff, 2, mean)
# View histogram of mean differences
hist(pred_diff_ckcs)
# Examine mean of difference
mean(pred_diff_ckcs)
## [1] -0.001871383
# View histogram of this
HPDI(pred_diff_ckcs, 0.97)
## |0.97 0.97|
## -0.01944913 0.01969255
# create new dataframe which contains results of all dogds
new_data2 <- df
# Now change one category to be different
new_data2$breed_group <- c("pug")
# Now get predictions from the draws of the models
pred_nd1 <- posterior_predict(model, newdata = new_data1)
pred_nd2 <- posterior_predict(model, newdata = new_data2)
pred_diff <- pred_nd1 - pred_nd2
pred_diff <- data.frame(pred_diff)
# Create mean of differences for each column (dog) of the dataframe
pred_diff_pug <- apply(pred_diff, 2, mean)
# View histogram of mean differences
hist(pred_diff_pug)
# Examine mean of difference
mean(pred_diff_pug)
## [1] 0.0005020827
# View histogram of this
HPDI(pred_diff_pug, 0.97)
## |0.97 0.97|
## -0.01413850 0.02107792
# create new dataframe which contains results of all dogs
new_data2 <- df
# Now change one category to be different
new_data2$breed_group <- c("other")
# Now get predictions from the draws of the models
pred_nd1 <- posterior_predict(model, newdata = new_data1)
pred_nd2 <- posterior_predict(model, newdata = new_data2)
pred_diff <- pred_nd1 - pred_nd2
pred_diff <- data.frame(pred_diff)
# Create mean of differences for each column (dog) of the dataframe
pred_diff_other <- apply(pred_diff, 2, mean)
# View histogram of mean differences
hist(pred_diff_other)
# Examine mean of difference
mean(pred_diff_other)
## [1] 0.001265779
# Create HPDI
HPDI(pred_diff_other, 0.97)
## |0.97 0.97|
## -0.02007916 0.02421905
# create new dataframe which contains results of all dogs
new_data2 <- df
# Now change one category to be different
new_data2$breed_group <- c("ret")
# Now get predictions from the draws of the models
pred_nd1 <- posterior_predict(model, newdata = new_data1)
pred_nd2 <- posterior_predict(model, newdata = new_data2)
pred_diff <- pred_nd1 - pred_nd2
pred_diff <- data.frame(pred_diff)
# Create mean of differences for each column (dog) of the dataframe
pred_diff_ret <- apply(pred_diff, 2, mean)
# View histogram of mean differences
hist(pred_diff_ret)
# Examine mean of difference
mean(pred_diff_ret)
## [1] -0.0002746355
# Create HPDI
HPDI(pred_diff_ret, 0.97)
## |0.97 0.97|
## -0.02206251 0.02043784
# Set individual priors
prior_int <- set_prior("normal(0, 1)", class = "Intercept")
prior_b <- set_prior("normal(0, 1)", class = "b")
prior_sd <- set_prior("normal(0, 2)", class = "sd")
prior_alpha <- set_prior("normal(4, 2)", class = "alpha")
# Combine priors into list
priors2 <- c(prior_int, prior_b, prior_sd, prior_alpha)
Increased adapt_delta >0.8 (0.9 here), as had divergent transitions
set.seed(666)
model2 <- brm(bf(slgCort ~ breed + (1 | visit),
sigma ~ breed),
family = skew_normal(),
prior = priors2,
data = df,
control=list(adapt_delta=0.9999, stepsize = 0.001, max_treedepth =15),
iter = 8000, warmup = 2000,
cores = 4,
save_pars = save_pars(all =TRUE),
sample_prior = TRUE)
## Compiling Stan program...
## Trying to compile a simple C file
## Running /Library/Frameworks/R.framework/Resources/bin/R CMD SHLIB foo.c
## using C compiler: ‘Apple clang version 17.0.0 (clang-1700.0.13.5)’
## using SDK: ‘MacOSX15.5.sdk’
## clang -arch arm64 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/Rcpp/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/unsupported" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/BH/include" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/src/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppParallel/include/" -I"/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/rstan/include" -DEIGEN_NO_DEBUG -DBOOST_DISABLE_ASSERTS -DBOOST_PENDING_INTEGER_LOG2_HPP -DSTAN_THREADS -DUSE_STANC3 -DSTRICT_R_HEADERS -DBOOST_PHOENIX_NO_VARIADIC_EXPRESSION -D_HAS_AUTO_PTR_ETC=0 -include '/Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/stan/math/prim/fun/Eigen.hpp' -D_REENTRANT -DRCPP_PARALLEL_USE_TBB=1 -I/opt/R/arm64/include -fPIC -falign-functions=64 -Wall -g -O2 -c foo.c -o foo.o
## In file included from <built-in>:1:
## In file included from /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/StanHeaders/include/stan/math/prim/fun/Eigen.hpp:22:
## In file included from /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/Eigen/Dense:1:
## In file included from /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/Eigen/Core:19:
## /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/library/RcppEigen/include/Eigen/src/Core/util/Macros.h:679:10: fatal error: 'cmath' file not found
## 679 | #include <cmath>
## | ^~~~~~~
## 1 error generated.
## make: *** [foo.o] Error 1
## Start sampling
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
## Found more than one class "stanfit" in cache; using the first, from namespace 'rethinking'
## Also defined by 'rstan'
## Warning: There were 1 divergent transitions after warmup. See
## https://mc-stan.org/misc/warnings.html#divergent-transitions-after-warmup
## to find out why this is a problem and how to eliminate them.
## Warning: Examine the pairs() plot to diagnose sampling problems
summary(model2)
## Warning: There were 1 divergent transitions after warmup. Increasing
## adapt_delta above 0.9999 may help. See
## http://mc-stan.org/misc/warnings.html#divergent-transitions-after-warmup
## Family: skew_normal
## Links: mu = identity; sigma = log; alpha = identity
## Formula: slgCort ~ breed + (1 | visit)
## sigma ~ breed
## Data: df (Number of observations: 73)
## Draws: 4 chains, each with iter = 8000; warmup = 2000; thin = 1;
## total post-warmup draws = 24000
##
## Multilevel Hyperparameters:
## ~visit (Number of levels: 2)
## Estimate Est.Error l-95% CI u-95% CI Rhat Bulk_ESS Tail_ESS
## sd(Intercept) 0.61 0.68 0.01 2.54 1.00 6523 9855
##
## Regression Coefficients:
## Estimate Est.Error l-95% CI u-95% CI Rhat Bulk_ESS Tail_ESS
## Intercept -0.07 0.48 -1.10 0.95 1.00 7882 8794
## sigma_Intercept 0.05 0.19 -0.30 0.45 1.00 10816 13304
## breedckcs 0.05 0.41 -0.73 0.92 1.00 13361 13495
## breedpug 0.26 0.48 -0.64 1.27 1.00 13708 13847
## breedret -0.02 0.32 -0.66 0.61 1.00 13048 14860
## breedother 0.15 0.32 -0.48 0.76 1.00 13071 14635
## sigma_breedckcs -0.11 0.36 -0.77 0.64 1.00 12868 14771
## sigma_breedpug 0.16 0.35 -0.48 0.90 1.00 13047 15225
## sigma_breedret -0.11 0.27 -0.63 0.41 1.00 12526 15927
## sigma_breedother 0.04 0.24 -0.44 0.50 1.00 12516 14554
##
## Further Distributional Parameters:
## Estimate Est.Error l-95% CI u-95% CI Rhat Bulk_ESS Tail_ESS
## alpha 4.17 1.39 1.86 7.24 1.00 18009 14160
##
## Draws were sampled using sampling(NUTS). For each parameter, Bulk_ESS
## and Tail_ESS are effective sample size measures, and Rhat is the potential
## scale reduction factor on split chains (at convergence, Rhat = 1).
loo_model2 <- loo(model2, moment_match = TRUE)
loo_model2
##
## Computed from 24000 by 73 log-likelihood matrix.
##
## Estimate SE
## elpd_loo -109.6 7.2
## p_loo 11.2 2.6
## looic 219.1 14.3
## ------
## MCSE of elpd_loo is 0.0.
## MCSE and ESS estimates assume MCMC draws (r_eff in [0.5, 1.1]).
##
## All Pareto k estimates are good (k < 0.7).
## See help('pareto-k-diagnostic') for details.
model <- add_criterion(model, "loo")
## Warning: Found 1 observations with a pareto_k > 0.7 in model 'model'. We
## recommend to set 'moment_match = TRUE' in order to perform moment matching for
## problematic observations.
model2 <- add_criterion(model2, "loo")
## Warning: Found 3 observations with a pareto_k > 0.7 in model 'model2'. We
## recommend to set 'moment_match = TRUE' in order to perform moment matching for
## problematic observations.
loo_compare(model, model2)
## elpd_diff se_diff
## model 0.0 0.0
## model2 -4.4 2.0
Model 1 is a better fit so keep this